Method of machining a thin-walled object



3,176,387 METHUD F MACHHNENG A THIN-WALLED UBEIECT Luis M. Argueso, In, White Plains, and Cyril S. Treacy, Scarsdale, N.Y., assignors to M. Argueso & (10., line, Mamaroneck, N.Y., a corporation of New York Filed Dec. 13, 1961, Ser. No. 79 22 (Ilaims. (til. 29-423) The present invention relates to a new and improved method of, and compound for preparing thin-walled objects such as honeycomb structures made of aluminum, stainless steel, plastics, glass and the like, as well as other structures having cores surrounded by thin walls, preparatory to performing a machining and cutting operation thereon.

In modern industries, structures of the above-referredto type require various machining operations including cutting, grinding, routing and the like. Many of these structures are composed of materials that cannot tolerate any substantial heating, so that the use of low temperature alloys and high melting point Waxes and the like are not suitable to fill the interstices and cores prior to a machining operation being performed thereon.

The principal object of this invention is to provide a method of, and compound for preparing thin-walled single or multi-core objects preparatory to performing machining operations thereon.

Another object of the invention is to provide such a method and compound that will permit the machining of thin-walled objects Without requiring the application of heat to remove the compound from the interstices or cores after a machining operation has been performed.

Still another object of the invention is to provide each a method and compound that will include the removal of the compound from the interstices or cores by an aqueous solution at substantially ambient temperature.

In one aspect of the invention, a thin-walled multi-core object, such as a honeycomb structure made up of thin aluminum sheet or the like, may have its voids filled with a compound including a water soluble wax such as polyethylene glycol having a predetermined molecular weight.

In another aspect of the invention, the polyethylene glycol may be admixed with a metallic carbonate and finely divided mica and/0r spun glass fiber and other similar materials. The resulting compound may be introduced into the structure by melting the same, which has no adverse effects on the unmachined article. However, it is often necessary to avoid the application of heat to the machined object because of adverse physical effects on the machined object.

The filled object may then be held in a conventional manner on the bed of a machine, and grinding, milling, routing and other operations may be performed on the object without damage to the fragile, thin Walls surrounding the voids in the object because of the support provided by the solid wax within the interstices or cores. Upon completion of the machining operations, the compound Within the interstices or cores may be removed by subjecting the object to an aqueous acid solution at room temperature which effectively removes all traces of the compound from the object and leaves no film of the compound on the walls of the object with no residual effect on brazing or other similar properties thereof. Accordingly, the machined object may be brazed or otherwise fastened to sheet material or the like, depending upon the end use to which the object is to be put.

In process handling, because of the fragile nature of the thin-Walled honeycomb core, damage is reduced considerably by filling the core with the compound prior to United States Patent 0 ice machining. The filled core can also be stored prior to machining in far less space than is required when the core is not filled. Due to the fragile nature of the core, it cannot be stored one on top of another without being filled with some kind of material, such as the compound of the present invention, which will prevent distortion of the core.

With the use of the compound and simple machining methods, the cutting time of the honeycomb core can be reduced to as compared with processes such as those employing an aqueous vehicle. In addition to aving valuable time in the cutting operation, the compound also allows the user to cut honeycomb core with a capital equipment investment of only 8% to 10% of that required for aqueous vehicle processes.

The above, other objects and novel features of the invention will become apparent from the following specification and accompanying drawing which is merely exemplary.

In the drawing:

I FIG. 1 is a perspective view of a piece of honeycomb material;

FIG. 2 is a view of a piece of honeycomb filled with the compound of this invention, in position and being machined by a routing cutter; and

FIG. 3 is a perspective view of a contour machined piece of honeycomb material after the compound of the invention has been removed from its cores or interstices.

Referring to FIG. 1, a honeycomb construction 10 is shown as composed of a plurality of alternating thin strips 11 and 12 of material such as aluminum, stainless steel, or other suitable alloy materials, and which may be made by forming the strips along a sinusoidal curve or modified sinusoidal curve in which latter form the general curve is formed of rectilinear portions 13. The strips 11 and 12 may be alternately reversed, held in contact and cemented or brazed along contacting lines or surfaces in order to form the honeycomb structure. Of course, the honeycomb structure may also be made of other materials such as cardboard, rubber, plastic, glass and the like. In fact, the method and compound of the present invention may be utilized in the machining of any thin-walled object where the walls are subject to damage incident to the machining operation.

It has been found that the admixture of predetermined quantities of water soluble waxes such as polyethylene glycol having molecular weights of from about 6,000 to 20,000, very finely water-ground mica and/or spun glass fiber and similar materials, and a carbonate, produces a compound that when molten can be poured into the interstices or cores of thin-walled objects and, upon cooling to room temperature, sets up, producing a hard and strong supporting medium that adheres to the thin walls and will not chip or flake when the object filled therewith is machined.

Examples of the compound are:

Parts by (I) Weight Polyethylene glycol (6,000 molecular Wt.) Very fine water-ground mica 10 NaHCO (precipitated, very fine) 20 Polyethylene glycol (6,000 molecular wt.) 60 Very fine water-ground mica 10 NaHCO (precipitated, very fine) 30 In'Examples I to VI lI, the'water-ground 'micafmay be replaced by spun glass fiber 10% or by a mixture of water-ground mica and spun glas fiber 10%.

' *e wse I pound may be completely removed from the interstices or cores by subjecting it to a five percent aqueous solution'of hydrochloric or acetic acid. While the aqueous solution of acetic acid is very effective with the compounds including NaHCO it has been found that the HCl aqueous solution is better for the compound employing CaCQ Increased removal of the compound vfrom the object may be accomplished by elevating'the temperature of the aqueous acid solution. The use-0f CaCO has been found t-obe' particularly useful because it does not release CO whenheated to the temperature concerned herein;

The resulting'machined object, after removal of the compound as above outlined, may be brazed to, sheets of material if so desired, and no deleterious after efiects of the compound will be present.

Although the various features of the new and' improved'method of, and compound for the treating of thin-Walled objects preparatory "to performing'machining operations onthe objects have been shown and described in detail :to fully disclose several embodiments of the in- V EIIilOIlyit' WlH be evident thatgchanges may be made 'in such details and certain features may beused without others without, departing from vention. V 7 7 'What is claimed is:

the principles of the in- 1. The method of machining athin-walledobject which comprises filling the voidsyof saidfobject with a water soluble waxj-ma'chining said object; and completely removing said wax with Water.

2; The method of machining a thin walled object which comprises filling the voids of said objectQwith awater soluble'wax; machining said object; and completely removing said wax by subjecting said object to an aqueous solution of an acid. r

3. Themethodof machining a thin-walledobject which comprises'filling the voids of said object with polyethylene I glycol; machining said object; and completely removing a Parts by 7 (III) I weight Polyethylene glycol (6,000 molecularfwt.) 55 Very-fine water-ground mica '5 N'aHCOg (precipitated very. fine) 40' V 1 l Polyethylene glycol- (4,000 molecular wt.) 70 Very fine water-ground mica .10 NaHCQ3 (precipitat d, very. fine) i 100 7 I M Polyethylene glycol'.(6,000 molecular wt.) 42 Very. fine'i water-ground mica 10- Chlorinated terphenylw (Aroclar 5460) 8 V NaHCO (precipitated, very fine) 40 Y Polyethylene glycol (20,000 molecularwt.) 12 Polyethylene glycol (6,000 molecular Wt.) 48 Very fine water-groundmica 10 ,7 NaHCO ;v (precipitated, very fine) "30 r j Y 7 i a '100 a (VII). 7 Polyethylene: glycol (20,000 molecular' wt.) 14 Polyethylene glycol (6', 000'moleculai' wt.) .4 56 Very fine Water-'ground'mica 10 NaHCO (precipitated, very fine) 20 I '7 7 i10 0 1ft (VIII) 7 I V Polyethylene glycol (20,000- molecular wt.) 14 Polyethylene glycol. (6,000 molecular wt.) 56 Very. fine water-ground mica '.f a .10 CaCO (precipitated,- very fine) L 20' Polyethylene glycol (20,000 molecular wt;) -14 Polyethylene glycol (6,000 molecular'wt.) 56 Spun gl'assfiber 10 CaCO (precipitated, very fine): 20

v (X) Polyethylene glycol (20,000 "molecular wt.) l4 Polyethylene glycol: (6,000 molecular Wt.) 56' Very fine'water ground micaand spun glass fiber"... 10. CaCO (precipitated, very fine) 20 said polyethylene glycol by subjecting sa'id object-to an aqueous solution of an acid. I

4. -The method of machining a thin-walledobject which comprises filling theJvoids of said object with a water soluble'wax; machining said 'object; and completely removing said waxvby subjecting said object to an aqueous solutionqof'acetic acid,

'5. The method of machining a thin-walled object'which comprises'filling the'voids-of said object with a water soluble wax; machining said object'; and completely removing said wax by subjecting said object toan aqueous solution of hydrochloricacid. v

' 6. The method of machining a thin-walled object which conip'risesfilling thevoids of 'said object with polyethylene aqueous solution of acetic acid. a

' 7. The 'm'ethod of machining a thin-walled object which comprises filling the voids of said objectwith polyethylene glycol; machining said object; and completely removing The compound. may be made simply by. heating the polyethylene glycol to a molten condition and stirring into it the' fin ely divided mica and/or spun-glass fiber,-and

metal carbonate until it is thoroughly mixed therein. The

molten compound maybe poured into the interstices of the honeycomb or cores. of thin-walled objects andiper erations may be performed on the filled'object. .When

the object has been properly. ma'chined,- the comsaid polyethylene glycol by subjecting said object to an aqueous solutionofhydroehloric acid.

'8; The method of machining athin-walled object which comp-rises filling he voids of said object with a compound including polyethylene glycol, finely divided mica and "precipitated sodium bicarbonate (NaHCO machining said object;'andcompletely removing said compound by subjecting said objectto anaqueous solution of'an acid.

'9. The method of-machinin'g' a thimwalled object which comprisesifillin'g' the voids of said objectw'itli a compound including polyethylene glycol,a mixture of finely divided mica and spun glass fiber, and precipitated sodium bicarbonate (NaHCO machining'said object; and completely' removing said 'compoun d'by subjecting saidobject to an aqueoussolution of an acid. a I

sa /sea? 10. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including polyethylene glycol, spun glass fiber and precipitated sodium bicarbonate (NaHCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of an acid.

11. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including polyethylene glycol, finely divided mica and precipitated sodium bicarbonate (NaHCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of acetic acid.

12. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including polyethylene glycol, finely divided mica and precipitated sodium bicarbonate (NaHCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of hydrochloric acid.

13. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including between about 42 to 70 parts by weight of polyethylene glycol having a molecular weight of about 6,000, parts by Weight of finely divided mica, and between about 20 to 40 parts by weight of sodium bicarbonate (NaHCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of an acid.

14. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including between about 42 to 70 parts by weight of polyethylene glycol having a molecular weight of about 6,000, 10 parts by weight of finely divided mica, and between about 20 to 40 parts by weight of sodium bicarbonate (NaHCO machining said object; and completely removing said compound by subjecting said object to an aqueous soltuion of acetic acid.

15. The method of machining a thin-Walled object which comprises filling the voids of said object with a compound including between about 42 to 70 parts by weight of polyethylene glycol having a molecular weight of about 6,000, 10 parts by weight of finely divided mica, and between about 20 to 40 parts by weight of sodium bicarbonate (NaHCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of hydrochloric acid.

16. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including 42 parts by weight of polyethylene glycol having a molecular weight of about 6,000, 8 parts by weight of chlorinated terphenyl, 10 parts by weight of finely divided mica, and 40 parts by weight of sodium bicarbonate (NaHCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of an acid.

17. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including between about 12 to 14 parts by weight of polyethylene glycol having a molecular weight of about 20,000, between about 48 to 56 parts by weight of polyethylene glycol having a molecular weight of about 6,000, 10 parts by weight of finely divided mica, and between about 20 to 30 parts by weight of sodium bicarbonate (NaHCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of an acid.

18. The method of machining a thin-walled object which comprises filling the voids of said object with a water soluble Wax having precipitated calcium carbonate (CaCO therein, whereby CO is not liberated when heating the wax preparatory to filling said voids; machin ing said object; and completely removing said Wax with water.

19. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including 14 parts by weight of polyethylene glycol having a molecular weight of about 20,000, 56 parts by weight of polyethylene glycol having a molecular weight of about 6,000, 10 parts by weight of finely divided mica, and 20 parts by weight of precipitated calcium carbonate (CaCOa), where CO is not liberated when heating the compound preparatory to filling said voids; machining said object; and completely removing said compound with water.

20. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including 14 parts by Weight of polyethylene glycol having a molecular weight of about 20,000, 56 parts by weight of polyethylene glycol having a molecular weight of about 6,000, 10 parts by weight of finely divided mica, and 20 parts by weight of precipitated calcium carbonate (CaCO machining said object; and completely rel roving said compound by subjecting said object to an aqueous solution of hydrochloric acid.

21. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including 14 parts by weight of polyethylene glycol having a molecular Weight of about 20,000, 56 parts by weight of polyethylene glycol having a molecular Weight of about 6,000, 10 parts by weight of spun glass fiber, and 20 parts by Weight of precipitated calcium carbonate (CaCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of hydrochloric acid.

22. The method of machining a thin-walled object which comprises filling the voids of said object with a compound including 14 parts by weight of polyethylene glycol having a molecular weight of about 20,000, 56 parts by Weight of polyethylene glycol having a molecular weight of about 6,000, 10 parts by weight of a mixture of finely divided mica and spun glass fiber, and 20 parts by weight of precipitated calcium carbonate (CaCO machining said object; and completely removing said compound by subjecting said object to an aqueous solution of hydrochloric acid.

References Qited in the file of this patent UNITED STATES PATENTS 1,280,892 Steenstrup Oct. 8, 1918 1,280,893 Steenstrup Oct. 8, 1918 1,332,445 Mershon Mar. 2, 1920 2,328,302 Simison Aug. 31, 1943 2,446,672 Sirp Aug. 10, 1948 2,810,738 Slack et al Oct. 22, 1957 2,905,064 Nielsen Sept. 22, 1959 2,955,951 Aelony Oct. 11, 1960 2,963,405 Seernuller Dec. 6, 1960 2,965,509 Hoffman Dec. 20, 1960 2,972,287 Rusinoif Feb. 21, 1961 2,972,548 Musser Feb. 21, 1961 2,984,897 Godfrey May 23, 1961 

1. THE METHOD OF MACHINING A THIN-WALLED OBJECT WHICH COMPRISES FILLING THE VOIDS OF SIAD OBJECT WITH A WATER SOLUBLE WAX; MACHINING SAID OBJECT; AND COMPLETELY REMOVING SAID WAX WITH WATER.
 22. THE METHOD OF MACHINING A THIN-WALLED OBJECT WHICH COMPRISES FILLING THE VOIDS OF SAID OBJECT WITH A COMPOUND INCLUDING 14 PARTS BY WEIGHT OFPOLYETHYLENE GLYCOL HAVING A MOLESULAR WEIGHT OF ABOUT 20,000, 56 PARTS BY WEIGHT OF POLYETHYLENE GLYCOL HAVING A MOLECULAR WEIGHT OF ABOUT 6,000, 10 PARTS BY WEIGHT OF A MIXTURE OF FINELY DIVIDED MICA AND SPUN GLASS FIBER, AND 20 PARTS BY WEIGHT OF PRECIPITATED CALCIUM CARBONATE (CACO3); MACHINING SAID OBJECT; AND COMPLETELY REMOVING SAID COMPOUND BY SUBJECTING SAID OBJECT TO AN AQUEOUS SOLUTION OF HYDROCHLORIC ACID. 